People often have problems of the rear vent pumping diff oil into the frame where in terminates and even as far as the firewall if you have extended it there like mine. Part of the problem is over filling the diff in the first place as the Jeep manual calls for the diff oil to stop 1/2" below the fill plug and not level with it like normal. But if you operate in high temperatures or even corner fast then you can still get a problem with it so below is a cure that I picked up.
Remove the hose from the vent and then un-screw it using a ring spanner as above. Do make sure that it is clean around the brake block as it will lift a bit once the vent is removed and dirt could fall into the axle housing. There is no need to touch the brake lines as they will remain connected and the vent just holds the block to the axle housing.
What you will cut off to shorted the vent to stop it picking up so much oil is the non threaded part of the vent at the very end which is arrowed above. Just place the vent into a vice clamping on the hex head like above and cut off just below the thread using a hack saw.
After the end has been cleaned up making sure the thread is clear of burrs just screw back in and your done. You don't even have to paint it as it will be coated in oil in no time at all!